Approximately 20 women who meet the inclusion criteria will be enrolled in this triple-blind, randomized, multi-center, two-year study to compare the efficacy of daily oral alendronate vs. intranasal calcitonin vs. placebo in increasing lumbar spine bone density in ambulatory postmenopausal women with low bone density. Alendronate will be triple-blinded and calcitonin will be administered open-label.